nside the massive stone exterior of St. John-St. Hugh Church in Roxbury, where the vaulted white ceilings and ornate walls are adorned with images of a European-featured Christ, something unexpected is stirring.

It can be heard in the beat of the music on Sunday afternoons, when the church choir is led not by the solemn groan of an organ, but with the celebratory spirit of another continent. It rustles in the clothes worn by the churchgoers who fill the sturdy wooden pews, and wear fabric woven with the intricate patterns, rich textures, and vibrant colors of the Igbo and Yoruba people of Africa.

It is present in the blessing ceremony blending Catholic and African ritual, when dozens of women dance and sing their way down the center aisle, moving slowly and gracefully toward the altar. There, as a priest sprinkles holy water over their heads, they sway from side to side, like a river rippling in bright shades of fuchsia, emerald, and turquoise.

It shines in the soul of this Mass, which draws more than 200 Nigerian Catholics every week, and has been fashioned by immigrants seeking to instill nuggets of their culture into a church more than 100 years old.

This fusion of religious ritual and immigrant traditions is fast becoming an integral part of parishes throughout the Archdiocese of Boston. The church community that Bishop Sean P. O'Malley will take charge of when he is installed as archbishop tomorrow is remarkably changed from the one that greeted his predecessors. Here, as in the rest of the country, newcomers from Latin America, the Caribbean, Asia, and Africa are replenishing and redefining the Catholic Church.

"These are the new children of the children. It's a matter of fact," said Didier Moise, 29, a Haitian-American who regularly attends the bilingual service in French and Creole at St. Angela Parish in Mattapan, home to a sizable Haitian community. "The church cannot be detached from that reality."

Immigrants from Portuguese and Spanish-speaking countries now constitute more than 350,000 of the two million Catholics in the Boston Archdiocese and account for the highest proportion of new growth, said the Rev. Christopher Coyne, the spokesman for the archdiocese.

That reflects a nationwide trend. Most newcomers to the United States are emigrating from countries with large Catholic populations, including Mexico, the Philippines, the Dominican Republic, Canada, Korea, and Vietnam, immigration specialists say. Nationwide, about 40 percent of recent legal immigrants identify themselves as Catholic, compared with about 24 percent of native-born Americans, according to the New Immigrant Survey, a 10-year study of immigrants across the United States.

"The bottom line is that there is a strong contingent of Catholics immigrating to the US. They are buttressing the numbers of Catholics here," said Guillermina Jasso, one of the study's principal investigators.

"These are fresh people for the American church, with a diversity of background, language, and culture," said Jasso. "The challenge for the Catholic Church is to maintain and invigorate its traditional ecumenical mission while taking people who are different and emphasizing what they have in common."

O'Malley, who speaks Portuguese, Spanish, and Haitian Creole, among other languages, has been attuned to that reality since the early days of his priesthood in Washington, D.C. There, his ministry focused on poor and disenfranchised refugees, undocumented immigrants, and other stuggling newcomers.

In Fall River, O'Malley's work with immigrant communities remained a mainstay of his ministry. In that diocese, he expanded the number of parishes serving the growing Latino community, and was often a vocal supporter of immigrants facing deportation.

Already, in the Boston Archdiocese, the archbishop-designate's reputation has resonated with immigrant Catholics, who hope his appointment is, in part, an acknowledgement of their growing presence and a sign that their voices will be heard.

"For many people, it's like a miracle," said Moise, who noted that many in the Haitian community were impressed to hear that O'Malley had celebrated Mass in Haitian Creole. "One of the problems people have is that they often feel on the sidelines when things are going on. Having a person who's conscious of our problems and concerns is an excellent choice."

The church as anchor

That instant rapport with immigrant Catholics may be crucial for O'Malley, who will be facing intense scrutiny and in need of allies as he tries to soothe a distressed archdiocese.

For the church, particularly the Archdiocese of Boston, where the sexual abuse crisis has disillusioned many of the faithful, the immigrant influx offers a rich source of Catholics who still view the church as central to their lives. During the waning days of Cardinal Bernard F. Law's leadership, some of his staunchest supporters came from among immigrant Catholics, especially in the Vietnamese and Latino communities.

For recently arrived immigrants navigating unfamiliar terrain, the church can serve as an anchor -- a familiar presence in a strange world -- and is often the first place a newcomer turns to for help.

"Over here, they are surrounded by a sea of Americans. The church is what keeps them together. Everything revolves around the church," said the Rev. John Morin, the vicar for the Haitian apostolate at St. Angela's. "They come to the church with unlimited confidence and trust. They trust us for everything."

However, each new immigrant group also brings unique customs, beliefs, languages, and histories -- and a challenge for the Boston church, once preponderantly Irish and Italian, and now faced with the task of ministering to a dizzyingly diverse group of Catholics.

In 1990, the Boston Archdiocese created the Office of Ethnic Apostolates to address the rapidly changing demographics. The office has grown to 36 ethnic apostolates, including a Hispanic Apostolate that covers 36 parishes. The congregants come from countries in every corner of the world, including Eritrea, Ethiopia, Laos, Indonesia, El Salvador, Colombia, and Guatemala.

"The church in Boston has always been an immigrant church," said Coyne. "At its beginnings, the Catholic community was formed by the Italian, Irish, and Germanic immigrants. As time went on, the church became a part of the melting pot of the United States. Now, we are continuing to be an immigrant church, but to different people."

The demographic shift is surfacing in churches throughout the archdiocese. Sometimes, in tiny details. Sometimes, in major adjustments.

Students now entering the seminary are required to learn Spanish, Portuguese, or a pastoral language other than English, said Coyne. In addition, many churches have added new statues representing saints with special significance for some immigrant groups. The Virgin of Guadalupe, for example, is revered by Mexican Catholics; while those from Cuba often pray to Our Lady of Charity.

An increasing number of churches now offer assistance with immigration, housing, job placement, and health problems, as well as spiritual counseling. At St. Angela's, for instance, volunteers work with parishioners who have AIDS, and help Haitian parents baffled by the parenting norms of this country.

"When you're dealing with new immigrants, you're not just dealing with language, but also with culture," noted Coyne. "Spiritual communication and ritual are expressed by more than just language. In parishes, where you have a large Hispanic or other immigrant community, their devotion, and their ritual are being recognized by statuary, by festivals, and by pageantry."

A cultural connection

At St. James the Greater in Chinatown, the lower chapel is decorated with hand-embroidered banners paying homage to Our Lady of China and embellished with the Chinese characters for the word "love." In a bow to the diversity within the Chinese community, Masses, religious education classes, and prayer groups are offered in Mandarin, Taiwanese, and Fujianese.

The church celebrates Chinese New Year with a special Mass dedicated to the ancestors of the parishioners, and a festival that features Chinese Lion dancing and martial arts demonstrations. Many of the parishioners travel from homes in the suburbs to attend the Chinese-language services, which they say offer a cultural connection missing in other churches.

"We don't feel like we're a part of the suburban churches. Here we have a common bond with our own people," said Mary Young, 52, who lives in Newton and attends Sunday Mass with her husband, Lai, 62. "When you're an immigrant, you can feel lost in this country. Part of the reason we come here is because of the community feel."

At St. Benedict's Church in Somerville, which was founded by three Irish nuns in 1819, the congregation is now predominantly Salvadoran. The annual parish feast -- now called "La Fiesta de San Benito" -- this year included Salvadoran folkloric dances, ranchera music, an array of Salvadoran food and handcrafts and pinatas for the children.

St. Benedict's, one the first parishes in the Boston Archdiocese to offer a Spanish-language Mass, was quick to grasp the importance of reaching out to the Latino population.

About 15 years ago, after Rev. John McLaughlin noticed a growing number of Latinos on the streets of Somerville, he started leaving notes on car windshields, in bars, and restaurants inviting the newcomers to his church. The notes read: "Usted esta en su casa." You are in your home.

"The Spanish reality is a strong one," said McLaughlin, who learned to speak Spanish and is called Padre Juan by Latino parishioners. "More and more Spanish people are coming in, and we try as much as possible to welcome them."

Juggling groups' needs

In the past, new ethnic groups often split off and formed their own church after their numbers grew large enough. However, many of the so-called ethnic churches were later shut down, falling victim to dwindling numbers and the financial constraints of the archdiocese.

Today, with the archdiocese facing even greater money woes, one church must often juggle the needs of several immigrant communities, in addition to the English-speaking members who are often long-time parishioners.

"Each of the various cultures wants to have its own services and own language. It can be hard to balance that," said Coyne. "Some people are threatened by the new people, new rituals, and new rituals coming in. Any change, especially when you're dealing with faith and ritual, is often difficult."

St. Rose of Lima in Chelsea, where earlier generations of immigrants came from Ireland, Italy, and Poland, now offers services in four languages: English, Cambodian, Vietnamese, and Spanish, reflecting the changing mix of newcomers.

At a recent Saturday evening Mass, the dimly-lit downstairs chapel was alive with the sounds of Spanish -- in the prayers recited by about 100 churchgoers from El Salvador, Guatemala, Colombia, and Mexico; in the songs played to a cumbia beat and performed by the Nuevo Renacer choir; in the handshakes and embraces accompanied by a wish for "Paz." A welcome sign, written in pale-blue chalk on the ground by the entrance, offered a greeting in Spanish: Bienvenidos.

Upstairs, inside the main church, the language was Vietnamese.

There, a small cluster of worshipers paid homage to a statue of the Virgin of La Vang, an incarnation of the Virgin Mary believed to have appeared in a Vietnamese forest 200 years ago. The prayers were hushed and melodic, the songs accompanied by the soft notes of an organ.

"We are one church in the sense that we are one building," said the Rev. Terrence Moran, who refers to himself a "gringo-riqueno," an Irish-American who speaks Spanish and has a fondness for the Latino culture. "It doesn't make sense to build a different building for each group. There are some things we can do together, but other times, people feel more comfortable with their own."

At St. Angela's, for example, the cavernous church is usually half-filled during English-language services, but is standing room only during the Haitian Mass on Sunday afternoon. The Mass, which usually runs longer than two hours, features a youth choir singing Haitian and French hymns and accompanied by congas, marimbas, and lively rhythms of the island's music.

"We could have done this all in English, and it would still be distinct from the Anglo liturgy. I say Anglo, not English, because language is not the important thing," said Moise. "When people hear about Mass in another language, they think it's just people who can't integrate in English. But this is a conscious choice. Being here on Sunday helps me grow spiritually."

"We are just filling our mission," said Moran. "Just take the line from Matthew 25: `When I was a stranger, you welcomed me.' The entire history of the church is really a history of first- and second-generation immigrants. If we stop taking in new people, it would curl up and die."